Question: Lisa went apple picking. She picked some apples on Saturday and $4$ more on Sunday. She picked $15$ apples in total. How many apples did Lisa pick on Saturday?
Answer: $ \begin{aligned}&{?} \text{ apples on Saturday}\\ +&\underline{ {4} \text{ apples on Sunday }}\\ =&{15} \text{ apples in total}\end{aligned}$ ${11}$ apples